14 replies to this topic

[stef]

well err im not on here as much as i used to be, but everytime i look in mini chat there seems to be a 'how can i make my mini go fast' or 'what first mods do i need'

so seeing as i had nothing to do i wrote this sort of guide about it.

i dunno if anyones done one or whatever, but i thought if it could be pinned here instead of put in the faq then maybe people would actually read it and not post these questions all the time.

its not really finished, i dont really know that much but i just wrote what i thought was right, so obviously im welcoming people that know more than me to change it or put new stuff in or delete stuff thats wrong etc.

or if its a bad idea then fair enough, didnt take me long anyway. and i know im probably wrong on some parts so im not looking to get flamed im just trying to help the forum.

ok so it wont let me upload a word file, so i'll just post it:



Right, so you’ve just bought your Mini, you realise that they aren’t the fastest machines in the world that you thought it would be, and you want to make it go faster. Well read on and you’ll find out. You could search, but that doesn’t work in the world of TMF, hence I wrote this so mainly Big Adam wouldn’t go mad and have to tell everyone to buy Vizards book. This is known as the yellow bible, which tells you everything you need to know about tuning your engine. If you’re as tight as me, you won’t buy the book. So here we go.

First steps:

If you have a 998, or in fact a 1275, you can do an engine swap. Easier for a 998 of course as you can drop a 1275 in, but if you already have a 1275 you will be looking at more high performance engines.
If, however, you don’t fancy doing this as it seems like too much work, there are plenty of other options. Please do not think that adding a few bits on to your 998 will mean you can outrun all the hot hatches on the road, because you cant. If you want to go faster than everyone else, then either have a huge wallet, or buy a different car. It’s the corners that count.
The first thing anyone will tell you is to get your Mini rolling roaded, or RR’d. This basically means your engine will be tuned to run perfectly throughout the rev range, and you will be surprised how much of a difference it can make to a standard engine. This will probably set you back around £40 an hour, depending on where you go. Allow for around 2 hours depending on what needs doing. Take note here, as if you plan on doing a lot of tuning, you’ll be on the rollers a lot.
If you have a bit more money, you can add a stage one kit. This comprises of a full exhaust system including manifold, an inlet manifold which is usually alloy, a new air filter and carb needle. You can buy an exhaust and then get all the other bits, but it is much cheaper and more efficient to buy a stage one kit. Minispares will be able to sort you out with a nice RC40 system, which come in twin and single box, the latter being slightly louder, but ever so slightly less powerful. This will cost around 170-180 pounds. BUT, you WILL need to have your mini rolling roaded afterwards to see the benefits, so you must budget for that.
The biggest mistake people make is not to get their car rolling roaded after a stage one kit, the needle supplied with the kit is probably close, but not right for your mini throughout all of the rev range, unless you have some sort of miracle Mini. Well all Minis are miracle but you know what I mean! You should see a quoted 20% power increase, and 12% torque increase. These are rough figures so don’t count exactly on them.
So that’s you’re first step. Your Mini is now thanking you as he or she can breathe much better!

Second steps:

So you’re enjoying the extra power you now have, but you have a taste for it now and want more.
A modified head is usually the next step, there are so many to choose from so you want to get it right. Depending on what engine you have, there are a few options. You could go to one of the main places like Minispares, Minisport, Morspeed, MED, etc, or go to somewhere like Bill Richards, Slarks, Swiftune etc.
The latter will get you a more custom head, the others tend to be off the shelf heads, so it won’t be tailored to how you would like. Not saying that they are bad, far from it, but if you want the best then you’ll have to pay a bit more than the others. The off the shelf heads usually come in ‘stages.’
Stage 1 is usually just a reconditioned unleaded head.
Stage 2 has slight port modifying and maybe slightly larger valves.
Stage 3 is widely used, has modified and polished ports, and larger valves.
Stage 4 is the same but larger still
Stage 5 is fairly mad.
Of course, you can find second hand heads about. You could get your own ported and polished, or find one and get that modified. It depends if you want a bolt on head or not really.
If you can find a 12g295 head, this will bolt straight onto a 998 no problems, probably the easiest second hand head to use. There’s also the 12g940, but if you wish to use this head on a 998, the block must be pocketed, which involves cutting out small sections of the block so that the exhaust valves do not hit the block and ruin your hard work.
For more info on different heads, look here:
http://www.theminifo...showtopic=19385

Third steps:

The wonderful world of camshafts. There are so many about, you have to decide what you want your engine for in order to choose the right one. You can of course put a cam in your engine before you get a head and see some gains, but it’s generally easier to put a cam in at the same time or after a head to see the best gains. A 998 cam can be changed in situ, so you do not need to take the engine out. It does mean cutting a hole in the inner wing though.
The cam manufacturers you will have heard of are of course Piper and Kent. However, Avonbar, Morspeed, Minisport etc all make their own cams too. Which you buy depends on how much lift you want from the cam. Of course more lift means a lumpier idle, which isn’t exactly what you want with town driving. So if you are using your Mini everyday, then consider this.
Swiftune makes the wonder cam, the sw5. This cam is recognised as being an extremely good all round performer for all sizes of engine, so look it up.

Fourth steps:

So after all that there’s still more to do. You can think about upgrading your clutch to a higher friction plate. There’s flywheels, consider a lightened one to help with your acceleration.
Depending on how many miles your engine has done, you’ll probably start having to double clutch down into second to stop it crunching. Baulk rings are your problem. Consider sending your gearbox to Guessworks on this forum for a refurb or rebuild. His prices are very good and his work is top notch. While you’re there, you can get him to fit a central oil pickup and maybe an xpin diff. Remember, your engine is only as good as its weakest part, so everything has to be taken into consideration. There’s no point in busting a stage 5 head and lairy cam on a 998 that’s done 100,000 as it just will not last.
Brakes are a major part of you’re tuning. There’s no point in having a million horses under you’re bonnet if you cant stop is there. Think about some uprated pads and new discs if you only have small mods, but think about new callipers for more mods. Most people go for 4 pots, and again these are available from most of the mini suppliers. Braided brake lines are also a good idea, they give a more solid feel to the pedal as they don’t expand as much as regular ones. Plus they look cool.

Remember that unless you say, install a head then get a cam in the next week or so, you should always rolling road after your new modification In order to see the best benefits.

[mike.]

If you can find a 12g295 head, this will bolt straight onto a 998 no problems, probably the easiest second hand head to use. There’s also the 12g940, but if you wish to use this head on a 998, the block must be pocketed, which involves cutting out small sections of the block so that the exhaust valves do not hit the block and ruin your hard work.

So anybody know what sort of advantage/gain i'd get if i put a 12G295 head on a stage 1'd 998?

Then what would i get with a 12G940 head?

[stef]

i cant remember the valve sizes on the 940, but from what i gather the 295 is a better head as it was intended for small bore applications.

to be honest i dont think theres a massive difference though.

[mike.]

ooo actualy while were on the subject of making a tuning guide thread, theres some great articles on the BMC forum written by keith calver. Theres a full topic about stage 1 kits then one about further optiond like cams and heads. Each of the articles is extremley informative and wuld be very useful in this thread.

Will it be ok if i put these artiles up if i say who there written by, when and where they're taken from?

[Ethel]

Tuning guide - Think a Mr Vizard did something similar, nearly 500 pages and it still leaves us asking questions.

12g 295 vs 12g 940 The 295 will drive better, the 940 (many different spec heads) will probably have the edge on all out power.

If you just bolted a head on the compression ratio could be well out so you may end up with less power or working engines than you started with. Think a Cooper 998 gave about 55 horses so you'd get a bit less than that. On a well sorted engine either head could easily give over 70bhp

[stef]

theres the answer u were looking for!

basically like i said im not exactly mr knowedgable so anyone can do what they want with this. would probably have been easier to just put up a sticky and then put links to calvers stuff, i didnt think about it at the time.

just new people are gonna want something short to read i guess.

[mike.]

Yeah, well i found calvers stuff pretty intresting. I think your write up is a good quick summary so good job on that.

But if anyone wants to know more about it and in more detail of these mods then calvers articles on BMC are great.

I'd post the links up except you have to be a BMC forum member to view them, so it'd kind of defeat the object of an easy run down of tuning options. Thats why i'd need to post them really...

[stef]

post em!

everyone always says search, but sometimes it can be hard finding exactly what you need, and to be honest i dont think a lot of people know that there even is an faq section

[mike.]

Right well heres the articles written by Keith Calver from the BMC Forum

they're both long but give great detail about mods. Both articles are for 998cc engines, not 1275cc.

Heres the first one about Bolt on tuning options i.e. Stage 1 Kits:

Engine - 998 Tuning, Bolt-ons

The 998cc engine is a very robust and tunable unit. It is also the most common engine found in standard Minis. Despite the lure of the much-advertised 1380cc alternatives, many simply want to get a little more from what they have at reasonable outlay.

Terminology:
MSC/MM - Mini Spares Centre/Mini Mania
ID - Inside Diameter
OD - Outside Diameter
BBU - Big Bore Unit (refers to all 1275cc-based units)
SBU - Small Bore Unit (refers to all sub-1275cc units, here the 998)
BHP - Brake Horse Power
LCB - Long Centre Branch

The 998cc engine is a very robust and tunable unit. It is also the most common engine found in standard Minis. Despite the lure of the much-advertised 1380cc alternatives, many simply want to get a little more from what they have at reasonable outlay.

The single biggest restriction on any standard Mini is the 'breathing apparatus' - anything that is connected to the induction and exhaust systems. The standard exhaust being the biggest culprit - it is desperately restrictive in the name of noise suppression and cheapness of manufacture. Oddly enough it also increases fuel consumption when tested over a better designed, free-flowing unit, so this is the place to start - NOT I stress the intake which is where many start in the belief that's the way to go. It is not. It is definitely the EASIEST place to start, and possible the cheapest - but will
net less gain for your money. Your best budget-verses-gain improvements should therefore be done in 'reverse' order - starting at the end of the exhaust then working your way back to the air filter.
Exhaust System.

The key here is not to use something that is too big, as this will actually loose power. Unfortunately it is a pitfall far too many fall into in the belief that 'biggest is best', and the recent crop of dirt-cheap, 2.0" systems. They are made 2.0" for two reasons - Mini owners seem to be impressed by the '2.0" exhaust' term, and the manufacturers believe they are making a more efficient system as it slides over the tail-end of most commonly used LCBs. For further reasons 'why', see 'Exhausts - sizing and styles'.
It is entirely possible to fit an efficient system on it's own to the standard manifold as Mini Spares/Mania can supply an adaptor for just such an application. This replaces the flared front down-pipe section from the cast iron manifold down to under the car to mate up with the RC40. They used to do just a short adaptor sleeve to fit the standard down-pipe but almost all folk found the flared end of their standard one had broken off once they'd got around to doing the job - so the adaptor was dropped as a pointless exercise.
1.625" internal bore is as big as you need to go on an SBU to get the very last drop of power out - even on a full-race engine. My recommendation here is the twin box RC40 - simply because in all the years it has been around - nobody has managed to better it's performance. And I've tried just about every last one that's come on the market. The only one that gets very close is the latest Millennium system from MSC/MM. The benefit of the Millennium exhausts for those who are aesthetically selective is the choice of 'exit' pipes and styles. The RC40 is available in single box form for those wanting a 'sportier' exhaust note, but is slightly less efficient than the full twin box - loosing a couple of BHP and shortens/lowers the torque curve.

Exhaust Manifold.

Progressing back along our route to power, the exhaust manifold is next. The standard iron one isn't too bad for an entirely standard engine, but is less efficient than the standard iron inlet manifold. The fact they are cast as one causes power losses on it's own by creating a severe, power robbing 'hot spot' in the inlet tract. Since separating them is only possible by destroying one or the other, loose the exhaust manifold.
Generally I use and highly recommend the Maniflow 'Cooper Freeflow ' exhaust manifold on SBUs. Originally developed by Maniflow owner Dave Dorrington when he was at Downton Engineering for the 970 S, it definitely has sufficient flow to cope with just about anything a 998 will could throw at it, and is easier to fit/seal than an LCB. Its design also suits the SBUs torque/power curve better than the commonly used LCB. And that's another common pitfall - fitting an LCB to the SBU. Some vendors sell what has become commonly termed the 'standard bore' LCB to fit everything - for exactly the same reasons they sell the 2.0" exhaust systems - it's what the misinformed Mini owners ask for, and there is a very cheaply made 'budget' example available that costs less than a Cooper Freeflow. This 'standard bore' LCB is in fact a 'medium bore' LCB developed for the BBU so is simply too big for the road-going SBU. In back to back tests I've done with this budget LCB and the Cooper Freeflow, I've always found the Freeflow gives better results. Not to mention the fact they last a hell of a lot longer through quality manufacture too!
I also use an LCB on SBU for the road, but this is the pukka small-bore LCB developed by Maniflow specifically for the SBU. The primary and secondary pipes are smaller, as is the tail-piece (fish-tail, 'Y'-piece). It does produce slightly better torque/power curves than the Freeflow but is marginally more expensive and less easy to seal off properly.

Inlet Manifold.

Although the standard iron inlet manifold is reasonably good, a well-designed and proportioned one will better it. The iron one's main problem is it's internal sizing - it's too big for the SBU. The MSC/MM
aluminum manifold out-performs the standard one by quite a margin in all areas, maximizing airflow and gas-speed within the very prohibitive space. The parameters for the manifold were to set to allow the use on the standard air filter case should this be required, and this has been met.
It also has the facility for water heating (not cooling as some folk believe). This is essentially to provide trouble-free running where cooler climates are to be experienced. Although having the intake temperature as low as is possible without actually freezing the fuel out of the air gives maximum torque/power, some manifold heating is required where climates are sufficiently cool enough to cause frost or heavy, cold misting. Cold wet air causing the biggest problems. Plumbing it into the system is a cinch - just take the hose off the heater tap and connect it to the left side of the manifold, than get a short piece of hose to re-connect the heater tap to the right side of the manifold (for further detailed information, see 'Inlet manifolds - single SU'').

Air Filters.

The standard air filter casing is surprisingly effective and efficient. Utilizing this with a replacement K&N air filter will provide pretty much all the airflow the engine will need, even when fairly well tuned. All that is needed to maximize the performance is to remove the hot-air 'snorkel', and drill a half-dozen three-quarter-inch diameter holes around the front underside of the casing. Ensuring these holes are OUTSIDE the cleaner element of course! The bonus of retaining the standard casing is the civilized noise level it provides in comparison to the cone/pancake type K&N…
It may look prettier - but that cone/pancake makes a mighty row. It's OK at idle, and tolerable when cruising at low speed, but any load or high- speed motoring creates an ear-bleeding din. Not only that, sorting the fuelling can be very arduous, AND recent testing has proven that this et-up actually LOOSES power over the aforementioned by around 5%! Now that's definitely not good.

The Holistic Answer.

The ingredients described above when added together comprise the 'stage one kit'. Although the above can be done one piece at a time if the budget is VERY tight, the complete stage one kit with all necessary gaskets and new carb needle required to provide correct fuelling only costs a comparatively small sum. The main benefit of doing it all in one go is actually reducing costs. Doing the job a piece at a time will involve re-tuning at each stage with the associated costs (carb needle, gaskets, etc.). Not to mention the aggravation of having to cut the manifolds apart - a very tiresome job! And you get the full power increase in one hit!
I developed the stage one kit for MSC many years ago to deal with just such tuning exercises. I used my every day 998 Mini. I took it to Peter Baldwin's rolling road,
optimized the performance of the standard unit then took some power readings. Off the rollers and up in the air, the Mini had the aforementioned components fitted then went back on the rollers. Again performance was maximized, the new power readings recorded. The needle type was kept as a standard, available as stock replacement so it was repeatable indefinitely. Filing one was no good as it's impossible to file two the same, let alone multitudes! The new ignition setting was duly noted also. The kit was then tried on several other 998 Mini with different engine specs/ages, and all results recorded and compared. The stage one kit gave essentially identical improvements on each engine.

Power Gains.

Using figures when discussing power gains is pointless. The improvements entirely depend on each individual engine's output prior to tuning. These vary considerably because of various factors - such as engine mileage, how well it's been maintained, low or high compression, pre-A+ or A+, and so on. We therefore use percentages, as these are more realistic and comparable.
I haven't tried testing each item as a replacement and seeing what power increases each made - the exercise would simply be too expensive. In fact it would cost something like three times the cost of a stage one kit! And the claims made by certain component manufacturers are unfounded. For instance - K&N would have you believe fitting a cone/pancake filter would unleash 6bhp. That would represent a gain of 14% all on it's own! Considering the WHOLE stage one kit gives 20% extra, and the exhaust is the most restricting component in the whole induction/exhaust system - the claim is impossible. It's more likely that replacing the exhaust would
net a 12% gain, the rest down to the induction.

My recommendation then is to go for the stage one kit first hit. If the budget is tight, borrow the money or save up - it won't break the bank and you'll get the best improvement in one shot with a great deal less hassle. The MSC/MM stage one kit contains all the right ingredients - K&N replacement air filter, high-performance water-heated inlet manifold, Maniflow Cooper Freeflow exhaust manifold, RC40 twin-box exhaust system, complete exhaust hanger kit, replacement carb needle, all gaskets and fitting instructions. It takes about 2.5 hours to fit taking things easy.

By way of a warning - some vendors advertise greater than 20% power gains. I'd like to see the proof of this as I've never seen more than 22% on one engine only where the exhaust was in particularly bad shape! I find it really hard to believe that a consistent 25% is possible. Only maybe on a one-off.

Useful part numbers:
C-STN17Complete stage one kit
RC40twin-box exhaust system
RC40-051Stainless steel rear box
RC40-060Stainless steel centre box and down-pipe for above
C-STR809RC40 rear box only
AN180VExhaust pipe required when fitting single rear box
RC40FKComplete RC40 fitting kit
C-STR816Cooper Freeflow exhaust manifold
C-STR817Small-bore LCB exhaust manifold
LDP1Front repair/conversion down-pipe for RC40 to standard exhaust manifold
C-AHT770Aluminum inlet manifold, 1.5" single SU carb
E2601K&N replacement air filter element
56-9320K&N cone filter
AJM601Exhaust manifold gasket
AEC2083Carb to manifold and throttle abutment plate gasket (3 required)
CUD1018AAU needle for stage one kit with replacement element air filter - non-modified casing
CUD1011AAM needle for stage one kit with replacement element air filter - modified casing (with holes drilled in) For full Millennium range of exhaust options, see stock listing.

Keith Calver
Article Date: Mar 05, 2001

[mike.]

And heres the second article and further tuning options on a 998. Including heads, cams and rockers:


Engine - 998 Tuning Further Options

Following on from the easily bolted on performance enhancing components out-lined in the stage one section, we need to consider where to go to get more power output.

Terminology:

MSC/MM - Mini Spares Centre/Mini Mania
BBU - Big Bore Unit (refers to all 1275cc-based units)
SBU - Small Bore Unit (refers to all sub-1275cc units, here the 998)
BHP - Brake Horse Power
CR - Compression Ratio

To improve engine out-put, you need to increase the engine's 'breathing' ability. The stage one kit deals with all the easily bolted-on external parts, and represents the best increase for investment. From here on in the power increases will cost commensurately more money. Power production of any engine, once the 'breathing apparatus' (induction/exhaust system) has been dealt with to cause no restriction - or certainly minimised where use of relatively standard major components such as the carb is concerned - is down to the cylinder head and camshaft. Both play a vital role in improving the engine's ability to breathe. The head through improved airflow by way of modification or replacement, the cam through increased valve-opening periods. How far these modifications and changes should go are dependant on what the engine is to be used for, or the power output required.

Books have been written on these subjects; here we're dealing with sensibly priced options for reasonable gain in engines that are used every day. Waxing lyrical about the virtues of this or that cam, and so-and-so's or such-and-such's cylinder heads are all well and good - but mean nothing without hard, practical proof. Consequently the following will be based on recent tests carried out by me to assess such changes.
Cylinder head.

After the stage one kit, this is the next easiest option as far as fitment goes. It's almost a 'bolt-on' part, but is a little more involved and a little more costly so is moved up a category.

The standard cylinder head is pretty restrictive where bigger power outputs are the main aim. To make appreciable gains it needs a fair amount of work done. Simply carrying out 'stage one' port, chamber and polish mods really don't do much at all for your money. The only sensible option is a standard head modified to 'stage three' spec, or a 12G295/12G206 Cooper head. Using a BBU 12G940 casting is an option - but not terribly practical (see 'Engine - 998 tuning, fitting a 1275 head').

The much coveted 12G295/12G206 heads are all-but non-existent realistically now. There are some about - most have been well used and abused, many cracked or modified into uselessness, with just a few, rare, un-molested examples of the species. But even a good example is likely to need complete refurbishment, particularly for the modern world where unleaded fuel is to be used. Suitable exhaust valve seat inserts will need fitting, new guides, seats re-cut, probably new valves, valve stem seals, and in all probability new valve springs. And then there's the machine-work needed to get it to work on your 998 - hefty re-facing to get CR to a sensible level since the standard head has a capacity of 24.2cc, the Cooper heads 28.4cc. That's a chunk to remove; charged by the cut it'll cost plenty. And having gone through all that - reliability is a problem - they're prone to cracking.

That leaves us with the 'stage three' spec modified standard head. MSC/MM sell heads modified by myself (Min Tec). The valve sizing is as that of the Cooper heads with all necessary port and chamber work carried out to give the best flow gains available within limiting criteria and inserted for unleaded fuel use. The main limitation is the combustion chamber - modifications are kept within sensible bounds so suitable chamber size is obtainable without excessive cost. To improve the chamber beyond that used would require large amounts of material to be removed off the head face. This generally breaks in to the rocker gear oil feed gallery necessitating this be brazed up, re-routed, and re-faced to true. The small improvement available simply doesn't warrant the extra costs incurred to do this. Even so, flow testing (results below) has shown that this style of stage three head all-but matches the inlet flow of the Cooper head, with better exhaust flow results so offers directly comparable performance, are available 'off the shelf', and are far, far more reliable. Particularly when comparing the figures below 0.350" lift as the cam/rocker combinations used only reach 0.340" lift.

STANDARD STAGE 3 COOPER 998
VALVE HEAD HEAD 12G295 HEAD
LIFT (in) INLET EX INLET EX INLET EX
0.050 16.7 16.0 19.7 18.3 17.9 16.0
0.100 32.5 27.1 36.4 35.3 38.2 29.7
0.150 42.6 38.1 51.1 49.6 51.4 41.9
0.200 50.2 47.0 62.8 57.2 65.2 52.5
0.250 55.8 51.4 71.4 61.4 73.5 57.2
0.300 60.4 54.6 78.9 64.5 81.1 61.0
0.350 63.8 56.9 84.3 66.8 87.0 63.6
0.400 65.3 58.9 88.9 68.9 91.8 65.1
Superflow 600 fully computerized flow bench. Tested at 25-in of water.
Flow test readings are average of all ports tested on one of each cylinder head types.
Camshafts.

Off the mark, a camshaft change to something more suitable will give you more 'bang for your buck' compared to a cylinder head. Having said that, it will not give initially as much power with the standard head as a stage three head will with a standard cam.

There is a multitude of camshaft options available, and most of them will have been tried by some one, somewhere. The problem is, many of them will have been tried in combinations that really didn't suit them - be this the wrong combination of parts, or used for the wrong application. It's no good fitting a camshaft that doesn’t start working until 5,000rpm shows on the tacho when you spend almost all your time driving in traffic. Likewise, a mild road cam isn't the best option for a circuit racer. Unfortunately, too many folk get lead down the wrong path here, and end up with a completely unsuitable cam for their particular situation. No more so than where road use is concerned.

I've run the gambit on just about every size of Mini engine in almost every possible situation along with a huge variety of camshafts. One thing stands tall above all the others - I have nearly always gone back to a relatively mild profile for roadwork. Something that gives it's best between 1,500-5,500rpm almost irrespective of engine size. The reason being this is where you tend to spend most of your time when driving on the road. Needing to run much over this means you either have an unsuitable final drive ratio, or just use the engine for scaring the local community at the weekend.

Considering the engine size and the operating range, this really does cut down camshaft choice to something in the 'mild' as opposed to 'wild' area. In my book the 997 Cooper profile takes some beating and would be my first recommendation to anybody wanting a decent road-burner. Or did until a few months ago - but more of that in a moment. It gives the right spread of power without being fussy or peaky. And the gain is pretty impressive over the standard item in an otherwise completely standard engine. Not only that, but it will idle smoothly and quietly and give emissions passing CO and HC readings. Something many of the 'modern' breeds of camshafts simply can't do without much frigging and fudging. With this in mind it was my first choice for the test I recently carried out for Mini Magazine where the criteria given matched almost exactly the aforementioned points.

Unfortunately I'd already built and installed the engine before I got my hands on one of Swiftune Racing's SW5 cams. This is the one I really would have liked to test, as it is something new that has been giving unbelievable results in practically all engines it's been tried in. I'm not allowed to give out specific details, what I can say is it is a 'modern' version of the 997 Cooper cam - which goes to prove that the old profile was pretty good in the first place and hard to beat by later 'developments'.
Rocker Gear.

It's pretty widely known that high-lift rockers don't give good results on 998s. The standard rocker gear, however, is a little short on what's required. Despite being 'accepted' as giving 1.25:1 ratio, they don't. You'd be lucky if the pressed steel versions give 1.23:1, and wildly lucky if the later sintered type gave 1.22:1 (they generally only manage a paltry 1.21:1). The 998 needs around 0.340" valve lift to make good use of the head mods - but not much more. The 997 camshaft has a lobe lift of 0.263". To get the required lift means rockers with a real lift ratio of 1.3:1 are needed, so I used the MSC/MM 1.3 roller-tip versions for the SBU. These give the required lift within a few thou.

As a footnote to this section, using the SW5 camshaft means sticking to the standard rockers as it develops more lift at the lobe.
Power Gains.

So what do we get after all our deliberation and hard work? The tests were carried out on the same rolling road I use for all my testing now that I live in the 'northern wilds' - GRV at Littleborough, home of the British Vita Racing Cooper Ss run by Harry Ratcliffe and Geoff Goodliffe (the 'G' & 'R' in the title). The exception was the stage one kitted Mini with a stage three head fitted. This was done by a good friend of mine, Steve Harris (ex-Downton man and well known Mini engine builder). But this doesn't matter over-much as actual bhp readings are not what we're looking for, as they are meaningless considering standard power outputs vary so much. It's the percentage we're interested in for comparative purposes.

A good, low compression 998 gives 30bhp. A good stage one kit (mod1) boosts this to 36bhp. The 997 Cooper camshaft and standard head (mod2) gave 42bhp and the 997 Cooper camshaft/stage three head/1.3 roller-tip rockers combination (mod4) gave 48BHP. Using percentages is a more relevant way of comparing results from different sources, so converting the aforementioned we get the mod1 kitted motor giving 20% more, mod2 giving a 40% increase over standard, and mod4 giving a whopping 60% over standard! Add into this equation the 43% increase that Steve Harris got by adding a stage 3 head to the stage one kit (mod3) on a standard engine and we've a full house of results -

Percentage power increase with each step:
Stage one kit +20%
Standard engine plus 997 Cooper cam +40%
Stage one kit plus Stage 3 head +43%
Stage one kit plus 997 Cooper cam, stage 3 head and 1.3 rockers +60%

A 60% increase is mighty impressive - especially when you consider it still idles sweetly, gives very low CO and HC readings at idle without any MOT/vehicle testing 'for-play', and actually gives more miles per gallon than standard! I largely suspect the Swiftune SW5 cam would give a few more bhp, but more importantly an increase in the over-all torque out-put - the most important factor for a street unit.
Useful part numbers:

C-AHT88 Stage three, unleaded SBU cylinder head assembly
C-AEG588 1.218" diameter nitrocarborised EN214N inlet valve
C-AEG589 1.040" diameter nitrocarborised EN214N exhaust valve
C-AJJ4037 Manganese-bronze valve guide - set of 8
C-AEA526 Dual valve spring set - 180lb
TAM2068 Lead-free exhaust valve seat inserts
ADU4905 Stem seals - latest top-hat/sprung type
GUG702506HG SBU genuine Rover head gasket
KC567M A+-drive type 997 Cooper profile camshaft
KC948 Pin drive type pp7 Cooper profile camshaft
C-AHT405 1.3 ratio roller-tip rockers, SBU only
AJM601 Exhaust manifold gasket
GUG705009VC Rocker cover gasket
GTG101 Thermostat housing gasket
88G221 Heater tap gasket

Keith Calver
Article Date: Mar 05, 2001

[mike.]

If you read those 2 properly there shouldn't be any questions needed really.

[stef]

of course there will be questions, there always is

kind of pointless me writing all that out now ive just read through that lol.

never mind, good to see i got most things right though i think.

[mike.]

Yeah you did, thats just a hell of a lot more detailed. Although yours wasn't ment to be lol.

Good thing about those articles is that they give you the actual power figures which is what everyone wants to know.

[stef]

i guess, but its still power figures that they got, like it says its totally dependant on the engine you have.

even if something like this was pinned on the forum, there would still be the japseye that asks how can he make his 998 go one billion miles an hour

[lemmingzappa]

I want to see this thread stickied !